Field of the Invention
The invention relates to a manufacturing method and a manufacturing apparatus of a liquid crystal display device having a photo alignment film.
Description of the Related Art
A liquid crystal display device, having the features of high display quality, thinness, lightness in weight, and low power consumption, is expanding application and variously used in a monitor for portable device such as a monitor for cellular phone and a monitor for digital still camera, a monitor for disk top personal computer, a monitor for printing and design, a medical monitor, and a liquid crystal television. With the expansion of the application, higher image quality and higher quality is required of a liquid crystal display device, and especially higher luminance caused by higher transmittance and lower power consumption is strongly required. According to the prevalence of a liquid crystal display device, there is also a strong demand for cost reduction.
Usually, a liquid crystal display device performs display by applying an electric field to liquid crystal molecules of a liquid crystal layer interposed between a pair of substrates to change the alignment direction of the liquid crystal molecules and accordingly change the optical characteristic of the liquid crystal layer. The alignment direction of the liquid crystal molecules without application of electric field is defined by an alignment film with rubbing treatment performed on the surface of a polyimide thin film. There are, however, some problems such as generation of static electricity or foreign substance due to the rubbing treatment and unevenness of the rubbing treatment due to an uneven substrate surface; therefore, a photo alignment method with no need to contact with a rubbing cloth is getting adopted. The photo alignment method is a method of giving alignment capacity to the surface of an organic film formed on the substrate surface by irradiating linearly-polarized UV lights to the surface of the organic film. An ultraviolet light (UV) irradiation device for photo alignment is disclosed in, for example, Japanese Patent Publication No. 2004-144884.